The<i>Solar Maximum Mission</i>Atlas of Gamma‐Ray Flares

Vestrand, W. T.; Share, G. H.; Murphy, R. J.; Forrest, D. J.; Rieger, E.; Chupp, E. L.; Kanbach, G.

doi:10.1086/313180

Cited by 78 publications

(72 citation statements)

References 27 publications

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“…Vestrand et al (1999) identified 258 flare events using Solar Maximum Mission observations. Among these, many are electron-dominated events with no clear signature of gamma-ray emissions (Rieger & Marschhauser 1990;Marschhauser et al 1994).…”

Section: Introductionmentioning

confidence: 99%

ON THE SPECTRAL HARDENING AT ≳300 keV IN SOLAR FLARES

Kong

Zank

et al. 2013

ApJ

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It has long been noted that the spectra of observed continuum emissions in many solar flares are consistent with double power laws with a hardening at energies 300 keV. It is now widely believed that at least in electrondominated events, the hardening in the photon spectrum reflects an intrinsic hardening in the source electron spectrum. In this paper, we point out that a power-law spectrum of electrons with a hardening at high energies can be explained by the diffusive shock acceleration of electrons at a termination shock with a finite width. Our suggestion is based on an early analytical work by Drury et al., where the steady-state transport equation at a shock with a tanh profile was solved for a p-independent diffusion coefficient. Numerical simulations with a p-dependent diffusion coefficient show hardenings in the accelerated electron spectrum that are comparable with observations. One necessary condition for our proposed scenario to work is that high-energy electrons resonate with the inertial range of the MHD turbulence and low-energy electrons resonate with the dissipation range of the MHD turbulence at the acceleration site, and the spectrum of the dissipation range ∼k −2.7 . A ∼ k −2.7 dissipation range spectrum is consistent with recent solar wind observations.

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Section: Introductionmentioning

confidence: 99%

ON THE SPECTRAL HARDENING AT ≳300 keV IN SOLAR FLARES

Kong

Zank

et al. 2013

ApJ

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“…The likelihood of observing a flare with gamma-ray emission can be estimated by using the long-term observations of the RHESSI 9 and the Gamma Ray Spectrometer (GRS) on SMM 30 . Flare occurrence with respect to time is used to predict the performance of GRIPS to account for the non-Poisson nature of flare events: an active region that produces one gamma-ray flare is likely to produce others as well.…”

Section: Long-duration Balloon Flights (Ldbfs)mentioning

confidence: 99%

The Gamma-Ray Imager/Polarimeter for Solar flares (GRIPS)

et al. 2012

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The balloon-borne Gamma-Ray Imager/Polarimeter for Solar flares (GRIPS) instrument will provide a near-optimal combination of high-resolution imaging, spectroscopy, and polarimetry of solar-flare gamma-ray/hard X-ray emissions from ~20 keV to >~10 MeV. GRIPS will address questions raised by recent solar flare observations regarding particle acceleration and energy release, such as: What causes the spatial separation between energetic electrons producing hard X-rays and energetic ions producing gamma-ray lines? How anisotropic are the relativistic electrons, and why can they dominate in the corona? How do the compositions of accelerated and ambient material vary with space and time, and why? The spectrometer/polarimeter consists of sixteen 3D position-sensitive germanium detectors (3D-GeDs), where each energy deposition is individually recorded with an energy resolution of a few keV FWHM and a spatial resolution of <0.1 mm 3 . Imaging is accomplished by a single multi-pitch rotating modulator (MPRM), a 2.5-cm thick tungstenalloy slit/slat grid with pitches that range quasi-continuously from 1 to 13 mm. The MPRM is situated 8 meters from the spectrometer to provide excellent image quality and unparalleled angular resolution at gamma-ray energies (12.5 arcsec FWHM), sufficient to separate 2.2 MeV footpoint sources for almost all flares. Polarimetry is accomplished by analyzing the anisotropy of reconstructed Compton scattering in the 3D-GeDs (i.e., as an active scatterer), with an estimated minimum detectable polarization of a few percent at 150-650 keV in an X-class flare. GRIPS is scheduled for a continental-US engineering test flight in fall 2013, followed by long or ultra-long duration balloon flights in Antarctica.

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“…However, a M2 soft X-ray flare is not typically a prolific source of 2.223 MeV line emission. In fact, the catalog of g-ray flares observed by the Solar Maximum Mission (SMM) collected by Vestrand et al [1999] shows that the fluence of the 2.223 MeV g-ray line for flares of class M5 or lower was very low. Therefore, the production of solar neutrons by soft X-ray flares of a low class (i.e., M2) may be considered small.…”

Section: Energy Spectrum Of Solar Flare Neutrons As a Function Of Thementioning

confidence: 99%

Estimation of the solar flare neutron worst‐case fluxes and fluences for missions traveling close to the Sun

Lario

2012

Space Weather

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[1] A method to estimate the total fluence of solar flare neutrons at a spacecraft traveling in the innermost part of the heliosphere (at heliocentric radial distances of <1 AU) is presented. The results of the neutron production and emissivity codes of Lingenfelter (1987a, 1987b) scaled to one of the largest solar neutron events ever observed at the Earth are used to derive a conservative estimate of the energy spectrum of neutrons emitted from the Sun after a large solar flare. By taking into account the survival probability of a neutron to reach a certain heliocentric distance, we evaluate the observed time-integrated spectrum of solar neutrons as a function of the heliocentric distance of the observer. By considering (1) a working relationship between the soft X-ray class of a flare and the flare's production of solar neutrons, and (2) the number and size of soft X-ray flares that may occur during a mission traveling close to the Sun, we compute an upper limit for the total fluence of solar neutrons at energies >1 MeV, >10 MeV, >100 MeV and >1000 MeV to which such a mission may be exposed. We apply this method to the Solar Probe Plus mission. Although our method gives a conservative estimate of neutron fluxes, the predicted mission-integrated fluence of solar neutrons at Solar Probe Plus is orders of magnitude below that of solar energetic protons.

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TheSolar Maximum MissionAtlas of Gamma‐Ray Flares

Cited by 78 publications

References 27 publications

ON THE SPECTRAL HARDENING AT ≳300 keV IN SOLAR FLARES

ON THE SPECTRAL HARDENING AT ≳300 keV IN SOLAR FLARES

The Gamma-Ray Imager/Polarimeter for Solar flares (GRIPS)

Estimation of the solar flare neutron worst‐case fluxes and fluences for missions traveling close to the Sun

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